The prison detention conditions endured by Bradley Manning – the US soldier who is alleged to have supplied classified government documents to WikiLeaks – have emerged.

For the last seven months, Private Manning, 23, has been kept in a cell six feet wide and 12 feet long, in solitary confinement at a maximum security military jail at Quantico, Virginia.

Lieutenant Colonel David Coombes, the lawyer defending him, pointed out that his client, who faces a 52-year sentence if convicted, is still being held on "Prevention of Injury Watch" for those deemed to be at risk of self-harm.

Friends of Private Manning say that this has become a means by the authorities to pressurise him into giving evidence against Julian Assange, the founder of WikiLeaks.

A typical day for Private Manning begins with being woken at 5am in the cell, which has a drinking fountain and a toilet. He is then allowed to put on his clothes, which he surrendered on going to bed the night before.

Under the rules, Private Manning is not allowed to sleep at any time between 5am and 8pm; if he does so, he is made to sit up or stand by the guards. He is allowed just one hour of exercise a day, even then not in the fresh air, but an empty room where he can walk in figures of eight. Any attempt by him to keep himself busy by, for example, doing press-ups, or sit-ups, is forbidden.

He is not allowed to associate with his fellow inmates and has never seen them, although he does occasionally hear their voices.

Private Manning is allowed to watch local television channels, for up to three hours on weekdays; sometimes more at weekends. But he does not have access to wider news coverage. He is allowed one book and one magazine at a time, from an approved list of 15, and is allowed approved visitors at prescribed times. Lt Col Coombes said the guards have, at all times, behaved correctly towards Private Manning. But, under the regulations, their conversations with him must be minimal.

The guards have to check every five minutes that Private Manning is ok, and he has to verbally confirm that he is alright. The same checks are continued during the night, and, if the guards cannot see Private Manning because he has pulled a blanket over his head (he is allowed blankets but not sheets or pillows) then they wake him up.

When Mr Assange was released from British custody on bail last week, awaiting extradition to Sweden to answer allegations of sexual assault, he vowed to continue leaking classified documents on WikiLeaks.